Investigation of initiation of gigantic jets connecting thunderclouds to the ionosphere

The initiation of giant electrical discharges called as "gigantic jets" connecting thunderclouds to the ionosphere is investigated by numerical simulation method in this paper. Using similarity relations, the triggering conditions of streamer formation in laboratory situations are extended to form a criterion of initiation of gigantic jets. The energy source causing a gigantic jet is considered due to the quasi-electrostatic field generated by thunderclouds. The electron dynamics from ionization threshold to streamer initiation are simulated by the Monte Carlo technique. It is found that gigantic jets are initiated at a height of ~18-24 km. This is in agreement with the observations. The method presented in this paper could be also applied to the analysis of the initiation of other discharges such as blue jets and red sprites.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

A Total Lightning Perspective of the 20 May 2013 Moore, Oklahoma Supercell

In the early afternoon of 20 May 2013, a storm initiated to the westsouthwest of Newcastle, Oklahoma. This storm would rapidly intensify into the parent supercell of the tornado that struck the city of Moore, Oklahoma. This article describes what contributions total lightning observations from the Oklahoma Lightning Mapping Array could provide to operational forecasters had these observations been available in realtime. This effort includes a focus on the GOESR pseudogeostationary lightning mapper demonstration product as well as the NASA SPoRT / Meteorological Development Laboratory's total lightning tracking tool. These observations and tools identified several contributions. Two distinct lightning jumps at 1908 and 1928 UTC provided a lead time of 19 minutes ahead of severe hail and 26 minutes ahead of the Moore, Oklahoma tornado's touchdown. These observations provide strong situational awareness to forecasters, as the lightning jumps are related to the rapid strengthening of the storm's updraft and mesocyclone and serve as a precursor to the stretching of the storm vortex ahead severe weather

An Overview of the Lightning - Atmospheric Chemistry Aspects of the Deep Convective Clouds and Chemistry (DC3) Experiment

Some of the major goals of the DC3 experiment are to determine the contribution of lightning to NO(x) in the anvils of observed thunderstorms, examine the relationship of lightning NO(x) production to flash rates and to lightning channel lengths, and estimate the relative production per flash for cloud-to-ground flashes and intracloud flashes. In addition, the effects of lightning NO(x) production on photochemistry downwind of thunderstorms is also being examined. The talk will survey the observation types that were conducted during DC3 relevant to these goals and provide an overview of the analysis and modeling techniques which are being used to achieve them. NO(x) was observed on three research aircraft during DC3 (the NCAR G-V, the NASA DC-8, and the DLR Falcon) in flights through storm anvils in three study regions (NE Colorado, Central Oklahoma to West Texas, and northern Alabama) where lightning mapping arrays (LMAs) and radar coverage were available. Initial comparisons of the aircraft NOx observations in storm anvils relative to flash rates have been conducted, which will be followed with calculations of the flux of NO(x) through the anvils, which when combined with observed flash rates can be used to estimate storm-average lightning NOx production per flash. The WRF-Chem model will be run for cloud-resolved simulations of selected observed storms during DC3. Detailed lightning information from the LMAs (flash rates and flash lengths as a function of time and vertical distributions of flash channel segments) will be input to the model along with assumptions concerning NO(x) production per CG flash and per IC flash. These assumptions will be tested through comparisons with the aircraft NOx data from anvil traverses. A specially designed retrieval method for lightning NO2 column amounts from the OMI instrument on NASA fs Aura satellite has been utilized to estimate NO2 over the region affected by selected DC3 storms. Combined with NO(x) to NO2 ratios from the aircraft data and WRF-Chem model and observed flash rates, average NO(x) production per flash can be estimated. Ozone production downwind of observed storms can be estimated from the WRF-Chem simulations and the specific downwind flights

Lightning location in a Colorado thunderstorm

The method of acoustically reconstructing lightning channels from thunder recorded with a small array of microphones (having a base line of about 5 m) is relatively slow (about 7 hours per lightning flash). We examine another method, which we have called thunder ranging, that does not provide as many points on the lightning channel but is considerably faster (about 2 hours per lightning flash). In this technique, the ranges of a source of a thunder pulse, .1-2 sec long, (also called a clap) to three, noncollinear microphones, separated by distances on the order of 1 km, are measured manually from an analogue oscillogram. From these ranges, the coordinates of the channel segment generating the pulse can be calculated. We discuss the sources and typical magnitudes of errors in this calculation. In the 1972 Colorado experiment, from which our data was taken, the error in the calculated location of a channel segment is typically within 15% of its range. We plot the location of twenty lightning flashes occurring between 18:7 MDT and 18:3 MDT in a multi-cell storm on 25 July 1972. These plots are superimposed on radar reflectivity contours in order to study ways in which lightning and storm structure are related. As in earlier acoustic studies (e,g Teer and Few,1974), the lightning channels are predominantly horizontal. They occur in a relatively thin layer; 4-5% of the calculated locations are between 4 km and 5 km above the ground; 7-8% are between 3.5 km and 5.5 km. The narrower layer is completely above the ° C isotherm in the cloud. Two other conclusions are tentative, since they are based on fewer observations, (1) The lightning channels seem to avoid regions of heavy rainfall 1.4 mm hr^-1, as determined by 1-cm radar) and often extend long distances into regions from which the echo is less than 3 dBZ. (2) Lightning is roughly aligned, having two possible correlations with the storm: the channels often parallel radar reflectivity contours, and they point from the region around the array spread toward regions into which a radar contour is expanding